1. Field of the Invention
The present invention relates to applicators and finishing tools for applying mastic or compound or plaster material to outside corner edges formed by drywall board sections such as are universally used in interior building walls.
2. Brief Description of the Prior Art
In one method for finishing an outside corner edge of two adjoining drywall board sections, a first layer of fast set compound or mastic material is applied, usually by hand, directly to the unfinished outside corner (of metal, plastic, or other conventional material as is well known in the art. Next, a corner is embedded onto the first mastic material layer by using a special pressing tool. The metal corner preferably has a sheet of paper material adhered to the outer surface thereof. Such paper-backed metal corners are generally referred to in the trade as "taped on metal corners". The paper backing typically extends a short distance beyond both vertical side edges of the metal corner bead such that they overlap adjacent portions of the two adjoining wall board sections. In accordance with the preferred technique, an amount of mastic material is squeezed out from beneath the side edges of the metal corner as the metal corner is embedded into the mastic material by the pressing tool. This excess material is hand wiped with a flat blade to finish and smooth the overlapping paper onto the wall board sections. It is desirable that the amount of mastic material squeezed out from beneath the metal corner not be excessive as this creates waste and is messy to properly finish.
In a second outside corner finishing method, a metal corner bead is secured to the outside corner using nails and/or screws after which a finishing coat of mastic or plaster material is applied to the outside corner (and metal corner bead). Various special tools have been developed for the application of mastic material to outside corners, and in particular outside corners which have been pre-fitted with a metal corner bead.
For example, U.S. Pat. No. 4,230,441 issued to J. D. Heronema discloses a rather complicated hand held tool consisting of a container for containing a supply of mastic material. The container has a first forward end with inwardly concave walls which conform to a 90 degree outside corner and a second, back end wall which is slidably movable towards the forward end when hand pressure is applied thereto. The sliding or piston movement of the back wall towards the forward end forces mastic material from inside the container through large openings in the forward end walls. The tool also includes wheels to guide the tool as it is moved along the outside corner and wipers with peripheral seals to spread and smooth the mastic material along the outside corner. It is readily apparent that such a complex tool is costly to acquire and that maintenance and clean up are time intensive. Also, a person using this hand tool may experience muscle soreness or fatigue in the arms, neck and/or back over prolonged periods of use in view of the amount of inwardly directed arm pressure and repeated stooping or bending required during use.
In another example, U.S. Pat. No. 4,907,955 issued to J. T. Snipes, there is disclosed a box-like device for containing a supply of plaster material and which includes a slot for dispensing the plaster material to a wall board adjacent a tacked on metal corner bead. The tool includes a guide member which engages a center ridge or upraised bead portion of the metal corner bead in order to keep the dispensing slot at a desired spaced distance from the apex of the outside corner.
Like the outside corner tool of Heronema described above, this tool also includes roller guide wheels and other adjustable parts which add to the expense and complexity of the tool. Further, this tool only permits the application of mastic material to one side of the outside corner at a time. Further still, this tool, like the tool of Heronema is directed for use in an outside corner finishing method wherein the outside corner has first been fitted with a metal corner, and in particular a metal corner bead, i.e., a metal corner having a center ridge or upraised bead portion. Accordingly, such tools are not suitable for use in finishing outside corners with beadless metal corners.
Accordingly there is a definite need for an improved outside corner finishing tool for use in drywall construction which overcomes the problems of the prior art. In particular, there is a need for an improved outside corner finishing tool for use in cementing a taped on metal corner to an unfinished outside corner.